Structured light generator and object recognition apparatus including the same

ABSTRACT

A structured light generator includes a light source configured to emit light, and a first meta optical device including a first metasurface including nanostructures having sub-wavelength dimensions that are less than a wavelength of the light emitted from the light source, the first metasurface being configured to form a distribution of light rays from the light emitted from the light source to thereby radiate structured light.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/426,646, filed on Feb. 7, 2017, in the U.S. Patent and TrademarkOffice, which claims priority from U.S. Provisional Patent ApplicationNo. 62/315,267, filed on Mar. 30, 2016, in the U.S. Patent and TrademarkOffice, and Korean Patent Application No. 10-2016-0112087, filed on Aug.31, 2016, in the Korean Intellectual Property Office, the disclosures ofwhich are incorporated herein by reference in their entireties.

BACKGROUND 1. Field

Methods and apparatuses consistent with exemplary embodiments disclosedherein relate to structured light generators for generating structuredlighting and object recognition apparatuses for sensing a shape or amotion of a three-dimensional (3D) object by using the structured lightgenerators.

2. Description of the Related Art

Recently, in order to recognize objects such as people or other things,accurately identifying the shape, location, motion, or the like of anobject by using precise three-dimensional (3D) shape recognition hasbeen emphasized. As one method in this regard, 3D sensing technologyusing structured light (a structured light system) has been developed,and thus, precise motion recognition has become possible.

In comparison with previously used light systems, such a structuredlight system is required to have a smaller size and higher resolutionwhen combined with various electronic devices. In order to generatestructured light, an optical component such as a diffractive opticalelement (DOE) is commonly used, and the volume of such an opticalcomponent is a factor that influences the precision degree of design andmanufacturing requirements.

SUMMARY

Exemplary embodiments disclosed herein provide structured lightgenerators for generating structured light.

Exemplary embodiments disclosed herein also provide e three-dimensional(3D) object recognition apparatuses including structured lightgenerators.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented exemplary embodiments.

According to an aspect of an exemplary embodiment, there is provided astructured light generator including a light source configured to emitlight; and a first meta optical device including a first metasurfaceincluding nanostructures having sub-wavelength dimensions that are lessthan a wavelength of the light emitted from the light source, whereinthe first metasurface is configured to form a distribution of light raysfrom the light emitted from the light source to thereby radiatestructured light.

The nanostructures of the first meta optical device may have forms thatare configured to realize a predetermined transmission intensitydistribution and transmission phase distribution with respect to theemitted light incident thereon.

The light source may include a light exit surface through which theemitted light exits; and the first meta optical device may have amonolithic structure and may be provided directly on the light exitsurface of the light source.

The nanostructures of the first meta optical device may have shapes andan arrangement that are determined such that a transmission intensitydistribution and transmission phase distribution with respect to theemitted light incident thereon are repeated.

The nanostructures of the first meta optical device may have the shapesand distribution such that two transmission phase modulation values areobtained.

The two transmission phase modulation values may be 0 and Tr.

A distance from the light source to the first metasurface may bedetermined such that a contrast of a structured light pattern formed bythe distribution of the light rays is a maximum.

The distance (d) from the light source to the first metasurface maysatisfy the following condition:

${d = {m\;\frac{2a_{1}^{2}}{\lambda}}},$wherein λ denotes the wavelength of the light emitted from the lightsource, a₁ denotes a period at which a same structure is repeated in thefirst meta optical device, and m denotes a natural number.

The structured light generator may further include a second meta opticaldevice provided between the light source and the first meta opticaldevice, and the second meta optical device may include a secondmetasurface configured to adjust a beam shape of the light emitted fromthe light source.

The first meta optical device and the second meta optical device mayshare a supporting substrate supporting the first metasurface and thesecond metasurface, and the first metasurface and the second metasurfacemay be respectively provided on different surfaces of the supportingsubstrate, the different surfaces facing each other.

The structured light generator may further include a third meta opticaldevice comprising a third meta surface configured to repeatedly form thedistribution of the light rays formed by the first meta optical devicein a predetermined angular space.

The first meta optical device and the third meta optical device mayshare a substrate supporting the first metasurface and the thirdmetasurface, and the first metasurface and the third metasurface may berespectively provided on opposite surfaces of the substrate, theopposite surfaces facing each other.

The nanostructures may have cylindrical shapes or polygonal prismaticshapes.

The nanostructures may have asymmetric shapes.

The first meta optical device may further include a substrate supportingthe nanostructures.

The nanostructures may include a dielectric material having a refractiveindex greater than a refractive index of the substrate.

The nanostructures may include a conductive material.

Some nanostructures among the nanostructures may include a dielectricmaterial having a refractive index greater than a refractive index ofthe substrate, and other nanostructures among the nanostructures mayinclude a conductive material.

According to an aspect of another exemplary embodiment, there isprovided a three-dimensional (3D) object recognition apparatusincluding: a structured light generator including: a light sourceconfigured to emit light; and a first meta optical device including afirst metasurface including nanostructures having sub-wavelengthdimensions that are less than a wavelength of the light emitted from thelight source, wherein the first metasurface is configured to form adistribution of light rays from the light emitted from the light sourceto thereby radiate structured light, and wherein the structured lightgenerator is configured to radiate the structured light in apredetermined pattern toward an object; a sensor configured to receivethe structured light reflected from the object; and a processorconfigured to analyze a shape or motion of the object by comparingpattern changes in the structured light radiated by the structured lightgenerator and the structured light received by the sensor.

According to an aspect of another exemplary embodiment, there isprovided an electronic device including the 3D object recognitionapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the exemplary embodiments,taken in conjunction with the accompanying drawings in which:

FIG. 1 is a conceptual diagram of structured light formed by ametasurface used in a structured light generator according to anexemplary embodiment;

FIG. 2 is a conceptual diagram illustrating examples of an opticalfunction that may be performed by a metasurface used in a structuredlight generator according to an exemplary embodiment;

FIG. 3 is a conceptual diagram illustrating an example of a form of abeam incident on each metasurface in FIG. 2;

FIG. 4 is a schematic cross-sectional view of a structure of astructured light generator according to an exemplary embodiment;

FIG. 5 is a perspective view of an example structure of a metasurfaceused in the structured light generator of FIG. 4;

FIG. 6 is a graph showing an example of a phase change distributioncaused by the metasurface of the structured light generator of FIG. 4;

FIG. 7 is a graph showing distribution of rays of light, that is, astructured light pattern, formed by a structured light generator havingthe phase change distribution of FIG. 6 as an intensity distribution inangular space;

FIG. 8 is a graph showing contrast of the structured light pattern ofFIG. 7 according to a distance between a light exit surface and ametasurface in the structured light generator of FIG. 4;

FIG. 9 shows an example of distribution of rays of light, that is, astructured light pattern, formed by the structured light generator ofFIG. 4;

FIG. 10 is a schematic cross-sectional view of a structure of astructured light generator according to another exemplary embodiment;

FIG. 11 is a schematic cross-sectional view of a structure of astructured light generator according to another exemplary embodiment;

FIG. 12 is a schematic cross-sectional view of a structure of astructured light generator according to another exemplary embodiment;

FIG. 13 is a schematic cross-sectional view of a structure of astructured light generator according to another exemplary embodiment;

FIG. 14 is a schematic cross-sectional view of a structure of astructured light generator according to another exemplary embodiment;

FIG. 15 conceptually shows that incident beams from respective lightsources are self-imaged in different forms by the structured lightgenerator of FIG. 14 to form complex structured light; and

FIG. 16 is a schematic block diagram of a structure of athree-dimensional (3D) object recognition apparatus according to anexemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplaryembodiments, examplesof which are illustrated in the accompanying drawings. Like referencenumerals in the drawings refer to like elements throughout, and sizes ofelements in the drawings may be exaggerated for clarity and convenienceof description. The present exemplary embodiments may have differentforms and should not be construed as being limited to the descriptionsset forth herein. Accordingly, the exemplary embodiments are merelydescribed below, by referring to the figures, to explain aspects.

Hereinafter, it will be understood that when an element or layer isreferred to as being “formed on” another element or layer, the elementor layer can be in contact with and directly formed on or in non-contactwith and indirectly formed on the other element or layer.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including,” when used herein, specifythe presence of other elements but do not preclude the presence oraddition of other elements unless specifically stated.

In addition, the terms such as “-or” and “-er” refer to a unit forperforming at least one function or operation, and the unit may beimplemented with hardware or software or a combination of hardware andsoftware.

FIG. 1 is a conceptual diagram of structured light SL formed by ametasurface MS used in a structured light generator according to anexemplary embodiment.

The metasurface MS may form a distribution of light rays from lightemitted from a light source LS. The light source LS may be a point lightsource such as a laser diode. With respect to an incident beam formed bythe light source LS, the metasurface MS may form a distribution of lightrays that proceed spatially. That is, light that is emitted from thelight source LS and forms one beam spot 10 is split into a plurality oflight rays by the metasurface MS, and each plurality of light rays formsbeam spot images 12 over a predetermined angular space. The beam spotimages 12 have various distributions determined by detailed conditionsof the metasurface MS, and are referred to as the structured light SL.

FIG. 2 is a conceptual diagram illustrating examples of an opticalfunction that may be performed by a metasurface used in a structuredlight generator according to an exemplary embodiment, and FIG. 3 is aconceptual diagram illustrating an example of the form of a beamincident on each metasurface in FIG. 2.

The metasurface may be realized as a beam shaper BS configured to shapea beam of incident light, a pattern generator PG configured to generatethe incident light in a predetermined beam pattern, a duplicator DPconfigured to duplicate a pattern formed by the pattern generator PG, acombination thereof, and the like.

The beam shaper BS may adjust a divergence angle, a beam section form, asize, or the like of light L₁ emitted from the light source LS. A beamL₂ shaped by the beam shaper BS is incident on the pattern generator PGand then is emitted as structured light SL′ in a predetermined patternto be incident on the duplicator DP. The duplicator DP may duplicate thestructured light SL′ formed by the pattern generator PG and thus mayform the final structured light SL.

In FIGS. 2 and 3, the function that may be performed by the metasurfaceis illustrated in order of the beam shaper BS, the pattern generator PG,and the duplicator DP, but exemplary embodiments are not limitedthereto. In order to form structured light, one or more of the beamshaper BS, the pattern generator PG, and the duplicator DP may be used,and the arrangement order may also be changed.

Various examples of a structured light generator using a metasurfacewill now be described.

FIG. 4 is a schematic cross-sectional view of a structure of astructured light generator 100 according to an exemplary embodiment, andFIG. 5 is a perspective view of an example structure of a first metaoptical device 120 used in the structured light generator 100 of FIG. 4.

The structured light generator 120 includes a light source 110 and afirst meta optical device 120 forming a distribution of light rays fromlight from the light source 110.

The light source 110 may be a laser light source and may include anemission layer and a plurality of reflective layers with the emissionlayer therebetween.

The first meta optical device 120 includes a first metasurface MS1including a plurality of nanostructures NS having sub-wavelengthdimensions less than a wavelength λ of light emitted from the lightsource 110. A height H of a nanostructure NS is less than the wavelengthλ of light emitted from the light source 110. Also, an arrangementdistance P between the plurality of nanostructures NS is less than thewavelength A. In FIG. 5, the nanostructure NS is illustrated as having acylindrical shape, but is not limited thereto. In some exemplaryembodiments, the nanostructure NS may have a parallelepiped shape, orhave a column shape having various cross-section shapes such as apolygonal shape, a cross shape, a star shape, circular shape, squareshape, elliptical shape, rectangular shape, an asymmetric shape, etc.Alternatively, the nanostructure NS may have an asymmetric shape.

Also, the first meta optical device 120 may further include a substrateSU1 supporting the nanostructures NS constituting the first metasurfaceMS1.

The substrate SU1 may include a dielectric material. For example, apolymer material, such as polycarbonate (PC), polystyrene (PS), orpolymethyl methacrylate (PMMA), SiO₂, or the like may be used to formthe substrate SU1.

The nanostructure NS may include a dielectric material, and may includea material having a refractive index greater than a refractive index ofthe substrate SU1. For example, one of single crystal silicon,polysilicon, amorphous silicon, Si₃N₄, GaP, TiO₂, AlSb, AlAs, AlGaAs,AlGaInP, BP, and ZnGeP₂ may be used to form the nanostructure NS.

Alternatively, the nanostructures NS may include a conductive material.The conductive material may be a highly conductive metal material wheresurface plasmon excitation may arise. For example, the nanostructures NSmay include at least one selected from copper (Cu), aluminum (Al),nickel (Ni), ferrum (Fe), cobalt (Co), zinc (Zn), titanium (Ti),ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), silver(Ag), osmium (Os), iridium (Ir), and gold (Au), and may include an alloyincluding one of those materials. In some exemplary embodiments, thenanostructures NS may include a two-dimensional material having goodconductivity, such as graphene, or conductive oxide.

Alternatively, some of the nanostructures NS may include a dielectricmaterial having a high refractive index, and other nanostructures NS mayinclude a conductive material. That is, some of the nanostructures NSmay include a dielectric material having a refractive index greater thana refractive index of the substrate SU1, and other nanostructures NS mayinclude a conductive material.

The nanostructures NS may each have transmission intensity andtransmission phases according to respective materials and shapes. Shapesof the nanostructures NS may be adjusted to adjust a phase or intensitydistribution of light passing through the first metasurface MS1. In FIG.5, all of the nanostructures NS illustrated have the same shape, size,and height. However, this illustration is just an example, and theexemplary embodiments are not limited thereto. For example, a horizontalor vertical size or a composition material of individual nanostructuresNS may be adjusted according to a location of the nanostructures NS toobtain a desired transmission intensity distribution or transmissionphase distribution. In order to obtain the desired transmissionintensity distribution or transmission phase distribution, a shapedistribution of the nanostructures NS at each location may be determinedwith respect to a predetermined group including the nanostructures NS.Also, a group of the nanostructures NS formed as such may be repeatedlyarranged with a predetermined period T. For example, FIG. 5 illustratesone group of the nanostructures NS, and the first metasurface MS1 mayinclude the illustrated group of the nanostructures NS that isrepeatedly arranged.

The first metasurface MS1 may have shapes and arrangement of thenanostructures NS determined to function as a pattern generator forlight emitted from the light source 110.

The first meta optical device 120 may be configured to have a monolithicstructure directly on a light exit surface 110 a of the light source110. When the first metasurface MS1 includes a group of thenanostructures NS repeatedly arranged with the predetermined period T, adistance d between the first metasurface MS1 and the light exit surface110 a may be determined so that a contrast ratio of structured lightgenerated by the structured light generator 100, that is, contrast, maybe maximum, and a thickness of the substrate SU1 may be determinedaccording to the determined distance d. The distance d may be calculatedusing the following equation (1):

$\begin{matrix}{d = {m\;\frac{2a_{1}^{2}}{\lambda}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

In Equation (1), A denotes a wavelength of light emitted from the lightsource 110, a₁ denotes a period at which the same structure is repeatedin the first meta optical device 120, and m denotes a natural number.That is, a₁ is the period T with which the group of the nanostructuresNS having the predetermined shape distribution illustrated in FIG. 5 isrepeatedly arranged.

The distance d denotes a condition where the contrast is maximum, and adistance between the first metasurface MS1 and the light exit surface110 a is not limited thereto. For example, the distance d may bedetermined by taking into account high contrast, complexity of astructured light pattern, and the like.

A volume of the structured light generator 100 may be greatly decreaseddue to the monolithically formed first meta optical device 120 beingdirectly provided on the light exit surface 110 a of the light source110. The first metasurface MS1 may be very thin having a thickness ofseveral microns or less, and accordingly, a thickness of the first metaoptical device 120 may be greatly decreased to tens of microns or less.As the whole volume of the structured light generator 100 greatlydecreases, limitations on manufacturing, for example, limitations on usein other electronic devices, may decrease, thereby enhancing pricecompetitiveness and broadening application ranges.

The first metasurface MS1 used in the structured light generator 100according to the present exemplary embodiment may have shapes and anarrangement of the nanostructures NS determined to serve as a patterngenerator. For example, shapes and an arrangement of the nanostructuresNS may be determined so that two phase modulation values with respect toincident light may be repeatedly shown. For example, the firstmetasurface MS1 may have two phase modulation values of 0 and π.

FIG. 6 is a graph showing an example of a transmission phase changedistribution caused by the first metasurface MS1 of the structured lightgenerator 100 of FIG. 4.

The letter X marked on a horizontal axis of the graph denotes aone-dimensional direction in which the nanostructures NS are arranged.Referring to the graph, a pulse train in which the transmission phasesof 0 and π repeatedly occur during a period of 0.5 um is shown, and aduty cycle of the pulse train is 0.5. The form of transmission phasedistribution implemented is an example, and shapes, arrangement, andmaterials of the nanostructures NS may be variously modified to form adesired structured light pattern.

FIG. 7 is a graph showing a distribution of light rays, that is, astructured light pattern, formed by a structured light generator havingthe transmission phase distribution of FIG. 6 as an intensitydistribution in angular space.

Referring to FIG. 7, the intensity distribution is not uniform at eachangular location. However, design factors of the first metasurface MS1may be adjusted to make the intensity distribution at each angularlocation uniform.

FIG. 8 is a graph showing a contrast of the structured light pattern ofFIG. 7 according to a distance between the light exit surface 110 a andthe first metasurface MS1 in the structured light generator 100 of FIG.4.

Referring to FIG. 8, a change in contrast from a minimum value to amaximum value is repeatedly shown. It may be seen that the maximum valueof the contrast repeatedly occurs when the distance d is an integermultiple of a predetermined value. The distance between the light exitsurface 110 a and the first metasurface MS1 may be determined by takingthe graph of FIG. 8 into account.

FIG. 9 shows an example of a distribution of light rays, that is, astructured light pattern, formed by the structured light generator 100of FIG. 4.

Bright spots are rays of light formed over angular space by the firstmetasurface MS1 from incident light emitted from a light source. Suchstructured light may be used to analyze a motion of an object, athree-dimensional shape, or the like by comparing a change of pattern ofthe structured light that occurs when being irradiated on and reflectedby the object. In this respect, as contrast indicating a differencebetween a bright spot and a dark portion increases, such an analysis maybecome easier. Also, a uniform intensity distribution over angular spacemay make the analysis easier.

FIG. 10 is a schematic cross-sectional view of a structure of astructured light generator 101 according to another exemplaryembodiment.

The structured light generator 101 includes the light source 110, asecond meta optical device 123 on the light exit surface 110 a of thelight source 110, and a first meta optical device 121 on the second metaoptical device 123.

The first meta optical device 121 includes the substrate SU1 and thefirst metasurface MS1, and the second meta optical device 123 includes asubstrate SU2 and a second metasurface MS2.

In the present exemplary embodiment, the second metasurface MS2 isdesigned to serve as a beam shaper shaping light from the light source110. That is, the second metasurface MS2 adjusts a divergence angle oflight emitted from the light source 110 to be incident on the firstmetasurface MS1. The first metasurface MS1 serves as a pattern generatorforming distribution of rays of light from incident light having adivergence angle and an incident beam form adjusted by the secondmetasurface MS2.

The first metasurface MS1 and the second metasurface MS2 each include aplurality of nanostructures having sub wavelength dimensions, whereinshapes and arrangement of the plurality of nanostructures are designedaccording to each of the above functions.

FIG. 11 is a schematic cross-sectional view of a structure of astructured light generator 102 according to another exemplaryembodiment.

The structured light generator 102 includes the light source 110, and ameta optical device 125 on the light exit surface 110 a of the lightsource 110. The structured light generator 102 according to the presentexemplary embodiment is modified from the structured light generator 101of FIG. 10 in that, according to the structured light generator 102, thesubstrate SU1 is shared by and supports the first metasurface MS1 andthe second metasurface MS2. That is, the meta optical device 125 has thefirst metasurface MS1 and the second metasurface MS2 respectively onboth surfaces of the substrate SU1. The second metasurface MS2 serves asa beam shaper and directly contacts the light exit surface 110 a. Thefirst metasurface MS1 forms distribution of rays of light from incidentlight having a divergence angle and an incident beam form adjusted bythe second metasurface MS2.

FIG. 12 is a schematic cross-sectional view of a structure of astructured light generator 103 according to another exemplaryembodiment.

The structured light generator 103 includes the light source 110, afirst meta optical device 131 and a third meta optical device 135, onthe light exit surface 110 a of the light source 110.

The first meta optical device 131 includes the substrate SU1 and thefirst metasurface MS1, and the third meta optical device 135 includes asubstrate SU3 and a third metasurface MS3.

In the present exemplary embodiment, the first metasurface MS1 serves asa pattern generator forming distribution of rays of light from lightemitted from the light source 110, and the third metasurface MS3 may bedesigned to serve as a duplicator duplicating the distribution of raysof light formed by the first metasurface MS1.

The first metasurface MS1 and the third metasurface MS3 each include aplurality of nanostructures having sub wavelength dimensions, whereinshapes and an arrangement of the plurality of nanostructures aredesigned according to each of the above functions.

FIG. 13 is a schematic cross-sectional view of a structure of astructured light generator 104 according to another exemplaryembodiment.

The structured light generator 104 includes the light source 110, and ameta optical device 137 on the light exit surface 110 a of the lightsource 110. The structured light generator 104 according to the presentexemplary embodiment is modified from the structured light generator 103of FIG. 12 in that, according to the structured light generator 104, thesubstrate SU3 is shared by and supports the first metasurface MS1 andthe third metasurface MS3. That is, the meta optical device 137 has thefirst metasurface MS1 and the third metasurface MS3 respectively on bothsurfaces of the substrate SU3. The first metasurface MS1 and the thirdmetasurface MS3 are designed to serve as a pattern generator and aduplicator, respectively.

The structured light generator 104 according to the present exemplaryembodiment is different from the structured light generator 103 of FIG.12 in that the first metasurface MS1 and the third metasurface MS3 areon both surfaces of one substrate SU3. Also, the substrate SU1 having athickness which may satisfy a condition of a distance between the lightexit surface 110 a and the first metasurface MS1 is provided between thelight source 110 and the meta optical device 137.

Examples of a structured light generator including two metasurfaces havebeen described thus far. Although examples in which the two metasurfacesare designed to serve as a beam shaper and a pattern generator,respectively, or serve as a pattern generator and a duplicator,respectively, have been described, examples of the two metasurfaces arenot limited thereto.

In addition, according to certain exemplary embodiments, more than twometasurfaces may be used. For example, a structured light generatorincluding three metasurfaces serving as a beam shaper, a patterngenerator, and a duplicator, respectively, may be implemented.

FIG. 14 is a schematic cross-sectional view of a structure of astructured light generator 105 according to another exemplaryembodiment, and FIG. 15 conceptually shows incident beams of a pluralityof light sources being self-imaged by the structured light generator 105of FIG. 14 to form structured light.

The structured light generator 105 includes a light source array 115,and a meta optical device 140 on the light source array 115.

The light source array 115 includes a plurality of light sources 115 ato 115 d. For example, the light source array 115 may be avertical-cavity surface-emitting laser (VCSEL) array.

The meta optical device 140 includes a first metasurface array 146 and asecond metasurface array 142. The first metasurface array 146 and thesecond metasurface array 142 may be respectively located on bothsurfaces of a substrate SU. A thickness d of the substrate SU may bedetermined to satisfy requirements for a distance between the firstmetasurface array 146 and the second metasurface array 142.

The meta optical device 140 may be integrated on the light source array115.

The second metasurface array 142 includes a plurality of secondmetasurfaces 142 a, 142 b, 142 c, and 142 d respectively facing theplurality of light sources 115 a, 115 b, 115 c, and 115 d. The pluralityof second metasurfaces 142 a to 142 d may serve as beam shapers shapinglight emitted from the light sources 115 a to 115 d, respectively.

The first metasurface array 146 includes a plurality of firstmetasurfaces 146 a, 146 b, 146 c, and 146 d forming distribution of raysof light from respective beams shaped by the second metasurfaces 142 ato 142 d.

Although all of the plurality of first metasurfaces 146 a to 146 d serveas pattern generators, patterns of structured lights SL_(a) to SL_(d)respectively generated by the first metasurfaces 146 a to 146 d may bedifferent from each other. That is, the first metasurfaces 146 a to 146d form image beams 12 to which an incident beam 10 emitted from eachlight source 115 a to 115 d is self-imaged, but form respectively uniquepatterns so that how the image beams 12 are distributed over space maybe different from each other. To achieve this feature, the firstmetasurfaces 146 a to 146 d may each include a plurality ofnanostructures having sub wavelength dimensions, but respective periodsT_(a), T_(b), T_(c), and T_(d) of repeatedly arranging the samestructure may be different from each other.

The structured light generator 105 is for generating complex andsophisticated structured light. The first metasurfaces 146 a to 146 dgenerating structured light having different patterns from each othermay be disposed to correspond to the light sources 115 a to 115 d,respectively, so that various patterns of the structured light SL_(a),SL_(b), SL_(c), and SL_(d) may be generated, and final structured lightSL which is more complex and sophisticated may be formed due tooverlapping of the generated patterns of the structured light SL_(a) toSL_(d).

Although an example of the structured light generator 105 in which thesecond metasurface array 142 serving as a beam shaper and the firstmetasurface array 146 serving as a pattern generator are provided on thelight source array 115 is shown, the structured light generator 105 isnot limited thereto. The structured light generator 105 may be modifiedto include a metasurface array serving as a pattern generator and ametasurface array serving as a duplicator.

FIG. 16 is a schematic block diagram of a structure of athree-dimensional (3D) object recognition apparatus 1000 according to anexemplary embodiment.

The 3D object recognition apparatus 1000 includes a structured lightgenerator 1200 which radiates structured light SL_(i) of a predeterminedpattern toward an object OBJ, a sensor 1400 which receives thestructured light SL_(r) reflected from the object OBJ, and a processor1600 which analyzes depth information, a shape, or a motion of theobject OBJ having a 3D shape by comparing pattern changes in thestructured light SL_(i) radiated by the structured light generator 1200and the structured light SL_(r) received by the sensor 1400.

The structured light generator 1200 may include a light source and atleast one metasurface and may take the form of one of the structuredlight generators 100 to 105 according to the previous exemplaryembodiments or a combination thereof.

The sensor 1400 senses the structured light SL_(r) reflected by theobject OBJ.

The processor 1600 may compare the structured light SL_(i) radiated onthe object OBJ and the structured light SL_(r) reflected from the objectOBJ with each other to analyze a 3D shape, a location, a motion, etc. ofthe object OBJ. The structured light SL_(i) generated by the structuredlight generator 1200 is a pattern in which bright and dark spots aremathematically coded to uniquely designate respective angle directionlocation coordinates. When such a pattern is hit upon a 3D object and isreflected, a pattern of the reflected structured light SL_(r) takes achanged form of the pattern of the radiated structured light SL_(i). 3Dinformation of the object OBJ may be extracted by comparing thosepatterns with each other and tracking a pattern for each coordinate.

The 3D object recognition apparatus 1000 may further include acontroller which controls an operation of driving the light source inthe structured light generator 1200, an operation of the sensor 1600, orthe overall operations of the entire 3D object recognition apparatus1000. In addition, the 3D object recognition apparatus 1000 may furtherinclude a memory, etc., which stores an operation program for 3Dinformation extraction to be performed in the processor 1600.

An operation result of the processor 1600, that is, informationregarding a shape and a location of the object OBJ, may be transmittedto another unit. For example, the information may be transmitted to acontroller of an electronic device in which the 3D object recognitionapparatus 1000 is used.

The 3D object recognition apparatus 1000 may be used as a sensor whichprecisely obtains 3D information regarding an object (e.g., an object infront of the 3D object recognition apparatus 1000) and thus may be usedin various electronic devices. For example, such an electronic devicemay be an autonomous driving device such as a driverless car, anautonomous vehicle, a robot, or a drone, an augmented reality device, amobile communication device, or an Internet of Things (IoT) device.

The structured light generator according to one or more of the aboveexemplary embodiments may form a distribution of rays of light(structured light) from light emitted by a light source by using ametasurface including nanostructures of a sub wavelength.

The structured light generator according to one or more of the aboveexemplary embodiments uses a structure in which a meta optical device isintegrated on a light source, and thus, is easy to miniaturize.

The structured light generator according to one or more of the aboveexemplary embodiments may use one or more metasurfaces and adjust adistance between a light source and a metasurface, and transmissionphase distribution and transmission intensity distribution of themetasurface, to generate structured light having a high contrast ratio.

The structured light generator according to one or more of the aboveexemplary embodiments may be used in a 3D object recognition apparatusconfigured to sense a precise motion and 3D shape of an object.

It should be understood that the exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exemplaryembodiment should typically be considered as available for other similarfeatures or aspects in other exemplary embodiments.

While one or more exemplary embodiments have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope as defined by thefollowing claims.

What is claimed is:
 1. A structured light generator comprising: a light source configured to emit light; and a first meta optical device comprising a first metasurface comprising nanostructures having sub-wavelength dimensions that are less than a wavelength of the light emitted from the light source, wherein the first metasurface is configured to form a distribution of light rays from the light emitted from the light source to thereby radiate structured light; and, a second meta optical device provided between the light source and the first meta optical device, the second meta optical device comprising a second metasurface configured to receive the light emitted from the light source, adjust a beam shape of the light emitted from the light source, and propagate the light having the adjusted beam shape to the first meta optical device.
 2. The structured light generator of claim 1, wherein the nanostructures of the first meta optical device have forms that are configured to realize a predetermined transmission intensity distribution and transmission phase distribution with respect to the emitted light incident thereon.
 3. The structured light generator of claim 1, wherein: the light source comprises a light exit surface through which the emitted light exits; and the first meta optical device has a monolithic structure and is provided directly on the light exit surface of the light source.
 4. The structured light generator of claim 1, wherein the nanostructures of the first meta optical device have shapes and an arrangement that are determined such that a transmission intensity distribution and transmission phase distribution with respect to the emitted light incident thereon are repeated.
 5. The structured light generator of claim 4, wherein the nanostructures of the first meta optical device have the shapes and distribution such that two transmission phase modulation values are obtained.
 6. The structured light generator of claim 5, wherein the two transmission phase modulation values are 0 and π.
 7. The structured light generator of claim 4, wherein a distance from the light source to the first metasurface is determined such that a contrast of a structured light pattern formed by the distribution of the light rays is a maximum.
 8. The structured light generator of claim 7, wherein the distance (d) from the light source to the first metasurface satisfies the following condition: ${d = {m\;\frac{2a_{1}^{2}}{\lambda}}},$ wherein λ denotes the wavelength of the light emitted from the light source, a₁ denotes a period at which a same structure is repeated in the first meta optical device, and m denotes a natural number.
 9. The structured light generator of claim 1, wherein the first meta optical device and the second meta optical device share a supporting substrate supporting the first metasurface and the second metasurface, and the first metasurface and the second metasurface are respectively provided on different surfaces of the supporting substrate, the different surfaces facing each other.
 10. The structured light generator of claim 1, further comprising a third meta optical device comprising a third meta surface configured to repeatedly form the distribution of the light rays formed by the first meta optical device in a predetermined angular space.
 11. The structured light generator of claim 1, wherein the nanostructures have cylindrical shapes.
 12. The structured light generator of claim 1, wherein the first meta optical device is directly disposed on and in contact with the second meta optical device.
 13. The structured light generator of claim 12, wherein the nanostructures comprise a dielectric material having a refractive index greater than a refractive index of the substrate.
 14. The structured light generator of claim 1, wherein a distance from the light source to the first metasurface is set to be inversely proportional to the wavelength of the light emitted from the light source, and directly proportional to a square of a period at which a same structure is repeated in the first meta optical device.
 15. The structured light generator of claim 12, wherein some nanostructures among the nanostructures comprise a dielectric material having a refractive index greater than a refractive index of the substrate, and other nanostructures among the nanostructures comprise a conductive material.
 16. A structured light generator comprising: a light source configured to emit light; a first meta optical device comprising a first metasurface comprising nanostructures having sub-wavelength dimensions that are less than a wavelength of the light emitted from the light source, wherein the first metasurface is configured to form a distribution of light rays from the light emitted from the light source to thereby radiate structured light in a predetermined beam pattern; and a third meta optical device comprising a third meta surface configured to duplicate the predetermined beam pattern of the structured light that is radiated from the first meta optical device in a predetermined angular space, wherein the first meta optical device is disposed between the light source and the third meta optical device, so that the light rays is directly propagated from the first metasurface to the third meta surface.
 17. The structured light generator of claim 16, wherein the first meta optical device and the third meta optical device share a substrate supporting the first metasurface and the third metasurface, and the first metasurface and the third metasurface are respectively provided on opposite surfaces of the substrate, the opposite surfaces facing each other.
 18. A three-dimensional (3D) object recognition apparatus comprising: a structured light generator of claim 1; a sensor configured to receive the structured light reflected from the object; and a processor configured to analyze a shape or motion of the object by comparing pattern changes in the structured light radiated by the structured light generator and the structured light received by the sensor.
 19. A three-dimensional (3D) object recognition apparatus comprising: a structured light generator of claim 16; a sensor configured to receive the structured light reflected from the object; and a processor configured to analyze a shape or motion of the object by comparing pattern changes in the structured light radiated by the structured light generator and the structured light received by the sensor.
 20. An electronic device comprising the 3D object recognition apparatus of claim
 18. 